Studies on structural and electrical properties of SrMnO 3− δ prepared in oxidising medium

Abstract

Oxygen deficient perovskite (SrMnO_3−δ) is formed by direct precursor (SrCO₃/Mn₂O₃) reaction in air at 1100°C. X-ray diffraction (XRD) results confirmed single phase polycrystalline ceramic having layered hexagonal crystal structure [lattice parameters a = 5·437(7) Å, c = 9·073(7) Å]. Fourier transform infrared results support perovskite phase. Field emission scanning electron microscopy reveals dense polycrystalline (1-9 μm) microstructure and TEM/SAED pattern exhibits excellent correlation with the hexagonal structure in good agreement with XRD results. Thermal analysis in oxygen medium indicated intrinsic oxygen non-stoichiometry in the sample with δ ∼0·12 under thermally activated condition with T1065°C. Complex impedance spectroscopy (CIS) results on electrical properties confirmed both the bulk (grain) and grain boundary contribution in different temperature ranges. An equivalent electrical circuit model using CIS response suggests cascading of parallel resistance-capacitance (‘RC’) combination in agreement with ‘brick layer model’. Direct current conductivity obeys thermally activated Arrhenius behaviour. Substantial conductivity enhancement (about five orders) occurs at 700°C when compared with ambient conductivity ∼10⁻⁸. Activation energy (∼1·0 eV) suggests intergranular activity due to O²⁻ ion migration via diffusion through lattice vacancy.

Keywords

Oxygen deficiency Microstructure Grain boundary Complex impedance Conductivity

Get full access to this article

View all access options for this article.

References

Subbarao

E. C.

: ‘Advances in ceramics’, in ‘Science and technology of zirconia’, (ed. Heuer

A. H.

and Hobbs

L. W.

), Vol. 3, 1; 1981, Columbus, OH, The American Ceramic Society.

Feng

and Goodenough

J. B.

: Eur. J. Solid State Inorg. Chem., 1994, 31, 663–672.

Goodenough

J. B.

, Ruiz-Diaz

J. E.

and Zhen

Y. S.

: Solid State Ionics, 1990, 44, 21–31.

Pagciak

, Chmielowiec

and Bujlo

: Mater. Sci. Poland, 2005, 23, 209–219.

Lacorre

, Goutenoire

, Bohnke

and Retoux

: Nature, 2000, 404, 856–858.

Kumar

, Kulandainathan

M. A.

, Raj

I. A.

, Chandrasekaran

and Pattabiraman

: Mater. Chem. Phys., 2005, 92, 303–309.

Mogensen

, Lybye

, Bonanos

, Hendriksen

P. V.

and Poulsen

F. W.

: Solid State Ionics, 2004, 174, 279–286.

Kilner

J. A.

and Brook

R. J.

: Solid State Ionics, 1982, 6, 237–252.

Battle

P. D.

, Gibb

T. C.

and Jones

C. W.

: J. Solid State Chem., 1988, 74, 60–66.

10.

Tichy

R. S.

and Goodenough

J. B.

: Solid State Set, 2002, 4, 661–644.

11.

Parras

, Alonso

, Gonzalez-Calbet

J. M.

and Vallel-Regi

: J. Solid State Chem., 1995, 117, 21–29.

12.

Denyszyn

J. C.

: ‘The dielectric behavior of perovskite-related manganese oxides with stretched bonds or multiferroic properties’, PhD thesis, University of Texas at Austin, Austin, TX, USA, 2006.

13.

Kennedy

B. J.

, Ting

, Zhou

, Zhang

, Matsuda

and Miyake

: J. Solid State Chem., 2009, 182, 954–959.

14.

Negas

and Roth

R. S.

: J. Solid State Chem., 1970, 1, 407–441.

15.

Lichtenthaler

: ‘Ordering of oxygen vacancies in reduced phases of CaMnO32x and SrMnO32x‘, PhD thesis, University of Oslo, Oslo, Norway, 2005.

16.

Caignaert

: J. Magn. Magn. Mater., 1997, 166, 117–123.

17.

Taguchi

, Hirata

, Kato

and Hirota

: Solid State Sci., 2009, 11, 491–495.

18.

: ‘POWD, an interactive powder diffraction data interpretation and indexing program’, J. Appl. Crystallogr., 1989, 22, 506–510.

19.

Thermo Nicolet: ‘OMNIC software library database for ideal perovskite‘, Thermo Nicolet, Waltham, MA, USA .

20.

Wei

, Nam

K. W.

, Kim

K. B.

and Chen

: Solid State Ionics, 2006, 177, 29–35.

21.

Roy

and Budhani

R. C.

: J. Appl. Phys., 1999,85, (6), 3124–3131. S. Du, J. Wang, H. Y. Zheng and F. Ma: React. Kinet. CataL Lett., 1993, 51, 415–421.

22.

Dutta

, Choudhary

R. N. P.

, Sinha

P. K.

and Thakur

A. K.

: J. AppL Phys., 2004, 96, 1607–1613.

23.

Brahma

, Choudhary

R. N. P.

and Thakur

A. K.

: Physica B, 2005, 355B, 188–201.

24.

Raistrick

I. D.

: In ‘Impedance spectroscopy’, (ed. Macdonald

J. R.

), 17–26; 1987, New York, John Wiley & Sons.

25.

Marco

R. D.

, Eriksen

and Zirico

: Anal. Chem., 1998, 70, 4683–4689.